1. Field of the Invention
This invention relates a thin film-structure and a method for producing the same, and more particularly the same structure and the same method suitable for parts constituting micro machines such as a micro actuator, cats, various sensors such as a micro sensor, various probes such as a sensor for a scanning probe-microscope, etc.
2. Description of the Prior Art
Micro machines, various sensors, various probes, etc. are needed to detect outward powers from a substrate surface, various proximity effects in a substrate surface, flows of liquids, voltages of other electronic circuits. Thus, thin film-structures, made by three-dimensionally deforming plane structures such as beams composed of various thin films through applied micro machining of thin film-forming techniques and micro processing techniques in manufacturing semiconductors, have been used.
In the past, a thin film-structure was produced as follows:
(1) A plane structure composed of two kind and over layers with different thermal expansion coefficients is formed and the three-dimensional thin film-structure was produced from the plane structure through its bimorph effect.
(2) A plane structure made of polysilicon is heated and deformed through current heating, maintained by a micro probe, to produce the three-dimensional thin film-structure.
(3) A thin film is formed by sputtering or the like and the three-dimensional thin film-structure is produced from the thin film by taking advantage of the remaining stresses in the film formation.
In producing the thin film structure by taking advantage of the above bimorph effect (the above (1)), the thin film structure has had layers with different thermal expansion coefficient after its production. Thus, on account of temperature change in using, the shape of the thin film structure changes with time through the bimorph effect in nearby room temperature.
In producing the thin film structure by heating and deforming the polysilicon (the above (2)), the thin film structure has difficulty having a desired strength and elastic limit, etc. because a material for it is limited to the polysilicon. Moreover, the plane structure requires to be held by a microprobe, which results in degradation of its productivity.
In producing the thin film structure by taking advantage of the remaining stresses in film-forming (the above (3)), its reproducibility is degraded and its shape change with time due to the change with time of the remaining stresses.
It is an object of the present invention to provide a thin film-structure having good productivity, reproducibility and good shape-stability after its production and a method for producing the same.
This invention relates to a thin film-structure composed of a three-dimensional deformed thin film made of an amorphous material having an supercooled liquid phase region.
This invention also relates to a method for producing a thin film-structure comprising the steps of:
forming on a substrate a thin film made of an amorphous material having an supercooled liquid phase region,
heating the thin film to a temperature within the supercooled liquid phase region and thereby deforming the thin film in a given shape, and
cooling the thin film to room temperature from the temperature within the supercooled liquid phase region to stop deforming the thin film and thereby forming the thin film-structure.
This invention addresses the above-mentioned problems by developing a new material constituting the thin-film structure and a method for producing them as follows:
The thin film-structure is formed of an amorphous material having an supercooled liquid phase region. First of all, a thin film is formed of the amorphous material and is heated to a temperature within the supercooled liquid phase region. Then, the thin film is deformed to a given shape at the temperature with in the supercooled liquid phase region.
That is, when the thin film made of the amorphous material having the supercooled liquid phase region is heated, it exhibits glass-transition phenomenon. Just then, the once solid and high rigid thin film becomes semisolid (supercooled liquid) and becomes in viscous flow of a viscosity of 108xe2x88x921013 Paxc2x7S. Thus, the thin film can be deformed through its weight as well as force from outside. Moreover, the thin film become soft at the region, so that it can be easily deformed to every kind of shape desired.
Then, when the thin film is cooled to a temperature below the supercooled liquid phase region, it becomes solid again and exhibits large stiffness. Thus, the thin film formed in a desired shape at the temperature within the region becomes solid and has large stiffness with its shape being maintained.
This invention has been realized through this inventors"" finding and attention of the above natures of the amorphous material having the supercooled liquid phase region and taking advantage of the natures.
According to the thin film-structure and the method for producing the same, only when the thin film made of the amorphous material is heated to a temperature within the supercooled liquid phase region, the thin film becomes in a viscous flow. Thus, the thin film can be easily deformed to form the thin film-structure. Since the thin film has a very large stiffness in a normal use nearby room temperature, the thin film dose not almost change in its shape.
Consequently, the thin film-structure having a high productivity, reproducibility and good shape-stability after its production can be provided.
Herein, the wording xe2x80x9csupercooled liquid phase regionxe2x80x9d is a temperature region from a glass-transition temperature (Tg) to a crystallization-starting temperature (Tx).